Adjustable support heads of the type indicated are typically used in connection with stands, tripods or other supports known within the technical sector in question to support optical or video/photographic equipment in one or more pre-selected spatial positions.
These heads are typically equipped with one or more articulated joints, for example of the spherical or cylindrical type, to vary the reciprocal position of the equipment supported by the head in relation to the support on which the head is fixed.
Generally, traditional support heads are equipped with special locking means that can be selectively activated to lock the joint in a desired position and, respectively, to release the joint so as to allow the equipment to be re-positioned.
In one of its more common forms, the locking means comprise a pin element, engaged by screwing into one of the joint elements and capable of being moved against another joint element so as to lock its relative movement owing to the friction exerted upon it.
Heads of this type have one serious limitation, however, due to the fact that, when the locking means are released, the equipment is completely free to move in relation to the support. This fact, particularly in the case of heads with a ball element, can be the cause of undesirable and sudden imbalances of the equipment supported by the joint with the consequent risk of the equipment and the entire support device falling and being damaged.
The manoeuvre to release the head must therefore be performed using both hands, one to operate the locking means and the other to provide adequate support for the equipment.
In order to overcome this drawback, support heads have been devised, also by the Applicant, that comprise friction means, arranged always to maintain a minimum level of friction between the elements of the joint, so as to prevent sudden and accidental movements on releasing the locking means. The friction means usually comprise one or more slides, produced of an appropriate material, mounted on a first joint element and loaded against the surface of a second joint element.
The optimum level of friction required between the joint elements is clearly dependent on the weight and size of the equipment supported, and so the force with which the slide is loaded against the second joint element is adjustable by means of a knob or control lever, separate and distinct from the control knob or lever of the locking means.
This, however, involves an undesirable complication of the shape of the support head, its dimensions and, above all, its internal mechanisms.